I would recommend somewhere reasonably central. You should be able to get good deals at a few places. I stay in town for work occasionally despite living reasonably close by and suggest the following from experience.

Pestana - Chelsea bridge. Usually good rates. Quiet but not too far from centre of town. Good rates usually.

http://www.tripadvisor.co.uk/Hotel_Revie...on_England.html

Grovesnor Hotel - Victoria - very central
http://www.tripadvisor.co.uk/Hotel_Revie...on_England.html

Prk plaza Westminster bridge
http://www.travelrepublic.co.uk/hotels/u...dev=t&gclid

You could also try the Cumberland.

It's really a case of looking for who has a good rate,
I'd recommend staying on the west side of London. Post up what you find if you are unsure and we'll help.

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Maxxed out!